Cellular networks were originally developed to provide primarily voice services over circuit switched networks. The introduction of packet switched 2.5G and 3G networks enables network operators to provide data services as well as voice services. Eventually, network architecture is expected to evolve toward all-IP networks providing both voice and data services. However, network operators have a substantial investment in existing infrastructure and would therefore prefer to migrate gradually to an all-IP network architecture to allow them to continue to use their existing infrastructure. At the same time, network operators recognize that there is a demand for high rate packet-data services. In order to provide high-rate packet data services, network operators may deploy hybrid networks wherein a high data rate (HDR) network is overlaid on an existing circuit switched or packet switched network as a first step in the transition to an all IP-based network.
A hybrid network that combines two or more networks with different signaling protocols and different air interfaces complicates signaling and session management. One example of a hybrid network combines an IS2000 radio access network providing voice and packet data services with a data only network, such as an IS-856-A High Rate Packet Data (HRPD) access network, providing high rate packet data services. A mobile station with an active packet data session in the HRPD access network may need to switch to the IS2000 network to perform some task, such as answer a voice call. The mobile station may stop listening to the base station in the HRPD access network and, under current standards, is not required to inform the HRPD access network. After switching from the packet switched network to the circuit switched network, the mobile station could power down without returning to the packet switched network. In either scenario, the HRPD access network may assume that the mobile station is still present and listening, or that it may return, and consequently reserve resources to serve the no longer present mobile station. If the HRPD access network receives incoming packet data for the mobile station, the HRPD access network may attempt to deliver the data to the mobile station, which is no longer present. The attempt to deliver the packet data will fail and the HRPD access network will eventually deduce that the mobile station is no longer listening. At that point, the HRPD access network will release resources and update the packet data serving node for accounting purposes. The packet switched network may send a request to a Mobile Switching Center (MSC) to page the mobile station in the IS2000 network before releasing resources. If the mobile station has powered down, the attempts to page the mobile station will be futile and will unnecessarily consume network resources.